<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .d1{
            width: 200px;
            height: 200px;
            background: red;

            /* 指定圆角的半径 */
            /* border-top-left-radius: 20px;
            border-bottom-right-radius: 50px; */
            /* border-radius: 20px 40px 60px 80px; */
            /* border-radius: 20px; */
            /* border-radius: 20px 60px; */
            /* border-radius: 20px 40px 60px; */

            /* 圆形：设置半径为宽高的一半 */
            /* border-radius: 100px; */
            border-radius: 50%;
        }

        /* 左半圆 */
        .d2{
            width: 100px;
            height: 200px;
            background: blue;
            border-radius: 100px 0 0 100px;
        }
        /* 上半圆 */
        .d3{
            width: 200px;
            height: 100px;
            background: green;
            border-radius: 100px 100px 0 0;
        }
    </style>
</head>
<body>
    <div class="d1"></div>
    <div class="d2"></div>
    <div class="d3"></div>
</body>
</html>